text:
What is the relationship between temperature, dew point and the formation of clouds?
What can you infer from the temperature / dew point values in this METAR?

EGJG 121630Z 09012KT 9999 SCT006 15/14 Q1015

I understand the temperature is 15 degrees and the dew point is 14, and I found this:

The temperature / dew point spread is low, so the risk of cloud
  forming is high especially if the temperature falls.

Why is the risk of clouds forming high, especially if the temperature is falling?

because it means that the air is almost saturated with humidity. a small drop in temperature and it is fully saturated, forcing condensation (cloud/fog) to take place.

As well as looking at one single METAR, it's useful to look at a series of METARs over time. If you see that the temperature-dew point spread (difference) is getting smaller over a few hours, then you can usually assume that the weather is getting worse, i.e. clouds and rain are likely.

The dew point is the temperature at which condensation (a cloud) forms.
If the dew point is the same as the temperature on the ground, then there will be fog.
The temperature usually decreases as the altitude increases. This is called the lapse rate. In general, the closer the dew point is to the ground temperature, the lower the cloud ceiling will be.

Your definition of dew point is not far from the mark, but could use improvement. A more accurate definition would include the statement that dewpoint is the point where condensation occurs at the same rate as evaporation, which is an important difference from what you sate. It is inaccurate to state that if temperature and dewpoint are the same there will be fog. Such conditions are conducive to fog, but will not necessarily result in fog.

@JonathanWalters Well, there is always some moisture in the air, so there will always be some "fog", even if it is a tiny amount.

I don't understand your statement; given there will a be moisture content, there will always be some fog?

This is not strictly correct, supersaturation can have an effect upon cloud formation - as can the presence of cloud condensation nuclei.

While not 100% accurate from a meteorological perspective this is basically the weather knowledge that's imparted in your typical private pilot ground school. It is quite literally "Close Enough For Government Work" :)

@voretaq7 While some may find misinformation such as "if the dew point is the same as the temperature on the ground, then there will be fog" to be satisfactory, I do not nor do not think it befits our industry.


text:
How to calculate the wind variation?
Given the:
True Heading = 070 degrees
True Track   = 061 degrees
True Air Speed = 120 knots
Ground Speed = 118 knots
what is the wind variation?
these are the steps I am taking to calculate the wind variation:
1 - put the true heading on top - the true heading is 070 degrees

2 - put the true air speed inside the little circle - the true air speed is 120 knots

3 - mark the drift ( true heading - true track) = (070 - 061) = 9 degrees on that line

4 - draw down to the ground speed (118 knots)

5 - bring the little blue circle back to zero

6 - rotate the disk so that the cross is on the central line

there I can see that the wind comes from 151 degrees at 19 knots.
Questions:
will this always be correct?
Could I have calculated it through a formula (without using the computer)?

The flight computer is just helping you do trigonometry, It's fairly simple to do in something like excel, or just a calculator on your phone which has sin/cos/atan functions.

Sure it can.  It's just vector math.
$$\vec{A} + \vec{B} = \vec{C}$$
If $\vec{C}$ is your ground speed vector and $\vec{A}$ is your airspeed vector (magnetic heading with true airspeed as a magnitude, then $\vec{B}$, the wind vector, can be solved for by
$$\vec{B} = \vec{C}- \vec{A}$$
Electronic flight computers and E6B apps for tablet computers/smartphones can do the same thing.  But it's nice to have some basic skills with a whiz wheel.

source: Stack Exchange

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text:
Why might an altimeter read incorrectly by 4000ft after sitting on the ground for some time?
My friend landed at Timaru Airport and when he put the aircraft into the hangar the altimeter reading was approximately 100ft [airport elevation is 89ft]. When he got back to go flying two weeks later the altimeter reading was over 4000ft.
He replaced the altimeter with a new one and now the same thing has happened again. Has anybody got any idea about what has happened?

Welcome to the site! Can you add any information about the type of aircraft? It might be relevant. And did he really just replace the instrument, or did an avionics mechanic examine it first?

Try switching to alt static source and see what happens.

This could become a safety issue. I think he better get to the root cause whatever it is.

Sound like a static tube blockage. But to rise to 4000ft the pressure in the static tube must decrease significantly. Is running close to the exhaust / engine? I'd thoroughly check the whole static system. Ryan Brunette gives good advice to start with.

Was the setting still showing the previous QNH or some nonsensical value? Was the previous QNH significantly different from current one?

No its about the same

This is how it works and I am surprised you switched the altimeter, unless I am missing something in your question. The altimeter reads the barometric pressure and should be set before you go flying. The airport will report the elevation and the knob on the altimeter can be turned till the altimeter is set to the correct altitude. You can confirm there is no blockage and the altimeter works correctly by getting the barometric pressure for the airport from the control tower or weather station, and it should match the barometric pressure numbers in the corner of the altimeter. Pressure changes on a daily basis and must be set each time. When we do a B check before flight, this is the exact procedure we do.
There is more information needed to properly diagnose this problem. With the lack of information I will continue on a couple of assumptions.
1) The altimeter has been bench tested and is serviceable
2) The altimeter system when installed in the plane does not match the local barometric pressure with the corresponding elevation
It was stated that the altimeter was replaced with a known good one. When this occurs the whole system must be pressure checked with a pitot-static test kit. This is a requirement since the system was opened up by replacing the altimeter. If this is not done the system is considered unserviceable. It appears this was not done.
To be complete I would check out the lowest point in the system for moisture and drain it if present.
Generally the procedures including connecting the tester to the pitot static system and taping (covering) all ports not connected. Then pressure is applied to the system, simulating different elevations. The airplane altimeter should match the testers simulated elevation within a certain + or -, for all specified elevations. Additionally, the rate of change of elevation is monitored for any abnormalities that may indicate a problem with any internal mechanisms.
Using the pitot-static tester is an absolute requirement in this situation.

An error from 100' to 4000' is roughly 125 mbar.  That would be a surface pressure of 875 mbar and the only thing that is going to produce that pressure deficit at the surface is a tornado (the record for a hurricane is 882 mbar).  That kind of error isn't just day-to-day pressure fluctuations and you probably cannot even correct for that much error with the kollsman knob if you were trying to just set field elevation.  Perhaps he mistakenly connected his altimeter to a vacuum line :)

I agree with you it is a lot. But we are lacking more info that is why I said it is important to get the local pressure. It was stated that the altimeter was replaced. If that is the case then it is required that the whole system be pressure tested or it would be considered unserviceable. Anytime a component is removed the system has become unsealed and requires a full test with a pitot static tester. To be complete I would check out the lowest point in the system for moisture and drain it if present. My concern is why wasn't the system pressure tested after the replacement.

I can edit my answer to include this?

Yea, feel free to include in your post.

The altimeter is in a Rans S7. Ultralight, so they are Non-TSO’d. Falcon  Wultrad.  I have both altimeter sitting on my desk and if I set them to the current QNH they wonder off after about an hour even if the QNH remains the same.

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text:
Why does the helicopter's nose go down when the cyclic is pressed forward (in a hover)?
Helicopters have hinges on top of the rotor mast, allowing the rotor to be tilted longitudinally (forward/aft) or laterally (sideways).
Why does the helicopter fuselage tilt up/down when the cyclic stick is moved longitudinally? It should not be influenced by what the rotor does due to the hinge, right?

You've edited the question so much that the existing answers no longer fit.  May I suggest that revert the edit, delete this question and start a new one?  But before you do, bear in mind that your opening assertion is wrong.  The fuselage does not adopt a new attitude immediately. There is a significant delay, which is what makes helicopters difficult to hover for beginners. The disc will fly into position immediately which creates a horizontal force which then pulls the fuselage into the new attitude. This is why rapid cyclic movements can cause a blade to strike the tail or cockpit.

@Simon yes you're right about the editing. Delete the question, what happens to the answers etc, does everything disappear?

@mins yes that's part of the answer isn't it, hinge offset aligning the fuselage with the rotor.

@mins This is getting messy. Many (perhaps most) helicopters don't have flapping hinges.  No helicopter with a teetering hinge also has flapping hinges.

Actually, I'm wrong. You can't delete a question with upvoted answers.  Not sure how you could handle this now.

@Simon: Right, I realize that teetering and flapping hinges have quite the same purpose. Deleting. That said, isn't centrifugal force part of the answer?

@Simon I can re-write, include the reference that I've found in looking it up, and mention that original question was different?

That might work.  Please consider the information already given and, the most important facts before you do so. 1.  The fuselage does not pitch down immediately. 2. The nose will pitch down until equilibrium between horizontal thrust and drag and between torque and gravity is reached. 3. The stabiliser will push the tail down as speed increases.  With this in mind, please be very clear about your remaining doubts.

I think you might be confused by what the hinges do.  In the example you show, the teetering hinge, which is only present in 2 blade rotors, causes both blades to tilt, or "teeter" or see-saw, together.  It is not possible for both blades to rise or fall in normal operations.  The feathering hinge is not really a hinge at all.  It is a bearing in the blade cuff which enables to blade pitch angle to change, caused by the position of the swash plate, by rotating the blade within it's cuff.
Consider a helicopter hovering in a no wind situation - simply because adding wind needlessly complicates the explanation.  I will also assume a counter-clockwise rotating rotor.  Simply reverse the explanation for a clockwise rotor.
The total thrust vector of the rotor is vertical, perpendicular to the centre axis of the disc.  It has a zero horizontal component so no force is applied longitudinally or laterally to the helicopter and it remains in a fixed position.
When you push the cyclic forward, the pitch of the blade at the leftmost position is increased, increasing the angle of attack and therefore the lift.  Due to precession, the blade rises at the back of the disc and falls at the front, tilting the entire disc forwards.
The total thrust vector remains perpendicular to the disc and since the disc is tilted with respect to the fuselage, is now comprised of horizontal and vertical components.  It is the horizontal component which accelerates the helicopter in the direction of the tilt.
So there is a force (lift) lifting the rear of the disc and lowering the front.  This force is transmitted through the rigid rotor drive shaft and pushes the nose down and pulls the tail up. Another way to think about this is that you are applying a force at the top of a lever, the drive shaft, which is above the centre of gravity and therefore causes the fuselage to rotate in pitch. The helicopter will continue to accelerate until the additional drag equals the horizontal component.
Helicopters also employ horizontal stabilisers which produce lift to push the tail down with increasing airspeed so the nose down pitch in cruise is reduced.
Therefore, pushing the stick forward and holding it at some attitude (when flying VFR you select a speed by adopting the nose down attitude for that speed which is learned from experience and practice followed by small trimming to hit the desired speed) will cause the nose to pitch down and the aircraft to accelerate until the trimmed speed is attained.

Then why does the helicopter not continue to tumble nose down, at low airspeeds when the horizontal stabiliser is not yet active?

Gravity. You apply a constant force which is eventually balanced by gravity trying to  pull the tail back down.

The helicopter is hanging from the hinge, with its centre of gravity underneath. Like having a pendulum in your hand, and then move it. During the initial acceleration the pedulum will stay behind the movement of your hand, but will catch up as soon as there is a constant velocity, and will remain swinging. I'll post a picture of what I mean tomorrow.

@Koyovis: Think of the rotor dragging the rest of the helicopter along. A equilibrium of drag, inertial and gravitational forces determines how big the tilt of the helicopter is.

That would explain why the nose goes down with increased airspeed. My question is: why does it go down immediately when the stick is moved forward, before the helicopter has picked up speed?

It doesn't.  See my comment under the question.

Huh.  A drive-by downvote with no comment.  How is that supposed to help quality?  Thanks for nothing!  (I don't care about -2, see my rep score) but I do care about knowing when I'm wrong.

@Simon There is no confusion on what the teetering hinge does. The answer you state is an incorrect wiki found in discussion panels: a constant torque about the CoG creates a constant angular acceleration about the CoG. Gravity going through the centre of gravity does not create a moment about the centre of gravity. The actual behaviour in your last paragraph is exactly what is not explained by acceleration.

@Koyovis Interesting. I did not get my answer from some Wiki. I learned it during training. I have no idea why you think that I  think that gravity acting through the CoG generates a moment, I do not.  I cannot see anything wrong with the last paragraph, it is entirely correct - I eagerly await your explanation of why it is not. This whole Q&A is confused since you open with a teetering hinge but seem to close with a semi or fully articulated head. I suggest that you edit the question to explain precisely what you are asking since the question as posed has been answered correctly.

@Koyovis Additionally, the answer you have posted does not fit the question.  If the question did not include a picture of a teetering head, or sought only answers for one, then fine. Alternatively, asking for each type of head would work but as it stands, it's a mess. To  make that concrete, perhaps you would like to consider what happens with a rigid head?

@Simon you asked what the - was for.

The question did not mention a hover condition, and it should have. It is answered partly by:

Forward acceleration, which indeed dips the nose down.
Forward velocity, which causes the nose to dip as airspeed picks up due to aerodynamic resistance. A negligible effect in the hover.

But there is a much more direct cause of fuselage tilt in the hover, which is mostly overlooked in the discussion panels: rotor hinge moment. Deflecting the cyclic causes the rotor tip path to deflect, due to flapping. Fuselage tilt is used as a feedback cue to cyclic input, by use of rotor hinge offset.

The rotating blades are subject to centrifugal forces, which pull the rotor hub in the plane of the rotor deflection. As soon as the rotor plane changes as a result of cyclic stick input, the resulting rotor hinge moment will change fuselage angle accordingly, providing the desired feedback cue.
A teetering rotor such as on Bell 212 and R-22 does not produce this mechanical rotor hinge moment. In flight, a helicopter is suspended from its rotor, with the Centre of Gravity underneath the centre of lift, unless the rotor can apply a hinge moment to the fuselage. With a rearward CoG and no hinge offset, the following could happen:

The helicopter has taken off vertically, nose tipped up first, and cyclic forward was input. If the rotor had a hinge offset the fuselage would tilt forward, but with a teetering hinge like in the question there is no centrifugal force acting on the hub, and fuselage position now depends only on CoG location. The upward nose angle has consumed some of the useful forward tilt of the cyclic stick. Visibility is impeded. Fuselage tilt provides no direct feedback of the cyclic position.

Fortunately there is an aerodynamic rotor hinge moment, created by the aerodynamics of flapping. The picture is from Helicopter Performance, Stability and Control by Raymond Prouty. It shows that at first, the rotor acts as a gyroscope and stays in its plane. But the blade feathering is referenced to the shaft, and angle of attack of the right hand blade is increased, left hand blade decreased. The rotor will then flap until it is perpendicular to the shaft. With teetering rotors, there is an indirect aerodynamic coupling between fuselage and rotor shaft. This provides the same cues as the hinge offset solution but at a slower rate.

I'm confused.  In your question, you show an image of a teetering hinge. This answer refers to hinge offset which is not possible with a teetering hinge for example on the R22 and B212 which you mention.  What type of rotor head are you asking about? Hinge offsets are only present in rigid and fully articulated heads.

A teetering hinge. There is an aerodynamic hinge moment, as the answer explains.

Ah, I see now.  I will have to find my (probably dusty by now) copy of Prouty. I've flown multiple teetering head types and was not aware of this!  Thank you.

It's an issue raised by a B212 pilot, flying a simulation model of ours. The question was very poorly phrased, but after looking it up in Prouty it made sense to me.

For the same reason you are pushed back into your seat when you press the throttle in your car but the speed hasn't increased significantly yet. Also known as horizontal acceleration. As soon as the rotor plane tilts forward, it applies forward thrust which creates forward acceleration. The rest of the vehicle is hanging below the rotor so its inertial mass delays its motion, causing it to swing behind. The angle is the arctangent of the horizontal acceleration divided by the vertical (i.e. gravity, 9.8 m/s^2 or 32 ft/s^2).

So when the acceleration has stopped and the helicopter has reached a constant velocity, does the nose come back up?

The nose comes back up if and when the horizontal stabiliser generates enough lift to push the tail down.

@Simon the acceleration does cause nose dip in the hover. There are rotor hinge moments that are generally overlooked, see my answer below.

No fancy drawings to accompany this, but...
When the cyclic is pushed forward, it is the same as pushing forward on the stick of an aircraft. The nose will drop. In the case of the helicopter, it drops because the pitch of the main blades is altered only on a portion of its arc, resulting in a lift on the back end and a push down on the front end.
One thing that makes a helicopter different from fixed wing aircraft is - it gets forward propulsion from directing the lift from the rotor disc slightly forward instead of straight up as in pure hover. So, to move out of hover, one puts the nose down to get forward propulsion and acceleration, and adds power and overall rotor pitch (collective) to counteract the loss of pure vertical lift from tilting forward.
The helicopter moves forward until it picks up enough speed that the  airflow from forward speed over the spinning rotor disc produces lift (the spinning disc now acts like a wing), and the helicopter enters what is known as forward flight mode - it now flies in a manner similar to a fixed wing airplane. Takes a lot less power to hold a helicopter in forward flight than in hover, because the forward flight airflow over the rotor disc is producing lift, instead of using the rotor's pull (powered entirely by the engine) to produce all of the lift.
However, the bird still depends on forward lift from the rotor disc to get forward propulsion instead of direct forward propulsion via a propellor as fixed wing aircraft use. So in forward flight, the rotor disc is tilted slightly forward to provide the propulsion.


text:
How can we operate wing bending tests?
I understand why we do wing bending tests. Now I want to learn more about the test. How is it performed?
I mean in what conditions, with what equipment and what are we expecting after we perform this test?

See here for more information.

This may be of interest

This would be another page of interest - http://www.popularmechanics.com/flight/g2428/7-airplane-wing-stress-tests/

First you need a wing that is representative of a flightworthy article.
Next, you need to collect the significant load cases. The most obvious one is that of maximum lift, but sometimes wings have failed even when they were strong enough to support the maximum bending moment. Torsion from aileron deflections and flutter are important, as is the in-plane bending moment from lift at high angle of attack.
Normally, the wing is placed in a rig and computer-controlled hydraulic jacks are used to pull on it, but this can be made much simpler. Below you see the ultimate strength test on the MIT Dedalus wing: Discarded soda bottles were collected, filled with a pre-calculated amount of water and hung from the main spar while the center of the inverted wing was lifted up by a forklift.

Load test on Dedalus wing. Yes, the guy with the Daedalus shirt is Mark Drela. Own work.
Besides the maximum strength tests, fatigue tests are of equal importance. Here a statistical load distribution (frequent low loads, infrequent high loads) is applied to the wing over thousands of hours. These tests stretch into the early operational phase of a design, such that the structure is cleared for more hours as the test progresses.

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text:
How does the drag coefficient behave at transonic and supersonic speeds for swept wing aircraft?
I was reading about wave drag and Concorde recently and found some contradictory information relating to drag. For example Wikipedia says:

Afterburner was added to Concorde for take-off to cope with weight increases that came after the initial design, and was used to push through the transonic drag barrier.

And they add the following image (it's sad that they don't mention what kind of aircraft it relates to):

But this image (from this article) suggest that aircraft with swept wings don't experience this sudden drag at transonic speeds, only later. Concorde has swept wings so it should experience max drag coefficient near mach 2 but it didn't have to use afterburners at this speed. How can it be? Were afterburners in Concorde necessary to break sound barrier, or only used for climbing?

Maybe someone knows some specific drag parameters at different speeds and would care to share, as I could't find anything specific...

Concorde afterburners were reducing overall fuel consumption.
To understand why there is a special drag penalty around Mach 1, please read this answer.
Now to your graphs in the question body. The first one with the steep drag peak at Mach 1 is for a straight wing which never was designed to fly trans- or supersonically. You do get such results, but only if you use the wrong design for the task.
The next graph shows how the drag peak is shifted to higher Mach numbers with sweep. This is true for the wing alone. This graph is most likely valid for a sheared wing: A straight, high-aspect ratio wing which is rotated around its vertical axis in the windtunnel. But an airplane is more than just the mid-span wing. Swept wings need a center section which adds drag which does not shift with sweep angle; see below for test results (source: Hoerner's Fluid Dynamic Drag, section XV).

Minimum drag coefficient over Mach for wings with aspect ratio 4 and different sweep angles
The last plot shows generic full airplane data, so it doesn't apply to a specific design but shows how things typically look like. Individual designs might still look quite different; for the F-16, for example, the drag coefficient triples between sub- and supersonic speed and stays roughly constant between Mach 1.3 and Mach 2.0 due to careful shaping which avoids the transsonic Mach peak almost completely.

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text:
Why did my plane descend nose down?
I was on a flight recently and the plane started to descend normally etc. However one cabin crew member randomly announced "remember if we have an emergency landing please leave all your belongings behind". I know this is said on auto announcement but I have never herd it said on a descent.
Anyway, suddenly the plane was going down nose down, controlled but lots of stuff rolled to the front. Several people were looking scared and I really thought/ knew it should not be nose down! This lasted about 1 minute and it then leveled out and landed fairly normally.
If that announcement wasn't made I could tell myself it was one of those things but cabin crew never let on and now I can't fly again but actually need to! I really thought we were crashing. Aircraft sounded normal but when it was nose down it was like the engines had gone really hushed.
I checked flightradar24 after we landed and there was a brief message flashed up that our flight was alerted by such and such a flight.. we landed at Newquay. The flight number was FR2954 on 12 Sep 2021 (ALC - NQY 03:40).
Can anyone say why this happened? I'm still shaken as I was always a terrible flyer. Something went on with that flight. I fly about 8 times a year and that has never happened! Why was the announcement made and why did the plane descend nose down?

Welcome to the site. Airplanes always descend by throttling back the engines and putting the nose down, it really can't be done any other way. I believe you when you say it was more exciting than usual, and it is unusual for them to remind people to leave their bags behind at that phase of the flight so it's possible the airplane experienced an emergency of some kind. Please keep in mind it was all fine in the end, chances are they were acting out of an abundance of caution.

Thanks... I just hope I can make myself fly again. Maybe the plane that alerted our flight was in trouble and we had to descend quickly !

@GdD: Actually it can.  If you've taken flying lessons that involved stalls, you've probably done an extreme version of it: point the nose up until you're on the edge of stalling, then add power to stay stable.  You can vary the power to climb or descend,  And pretty much all airplanes do the last part of landing in a nose-high attitude.  In a single engine plane, nose down landing can get you a prop strike.

I'm well aware of that @jamesqf, it is not a method for descent in an airliner, which has been asked and I have answered such here: https://aviation.stackexchange.com/questions/79236/is-it-practical-to-intentionally-stall-an-aircraft-to-execute-a-fast-controlled/79241#79241

@GdD: But you wrote AIRPLANES, not airliners.  Airliners are only a small subset of airplanes.  I doubt whether many of us here fly airliners, or ever want to.  (Comments from actual airline pilots would be welcome :-))  I've certainly seen airliners descending in a nose-up attitude, and certainly they nose is up at touchdown - do a search for pictures.

I've never seen or heard of anyone using a fully developed stall to descend outside of airshow routines @jamesqf, as for the landing flare that's a very different circumstance.

@EliseBarker I’ll just point out that your flight had a (brief) moment of something slightly unusual happening and landed 100% safely and normally. If anything, it sounds reassuring to me that something can be different, and it’s still incredibly safe!

This question was so confusing for me to read, because up until I started reading the answers, I was under the impression that OP was the pilot of that flight. Not a passenger :)

@GdD: Did I say anything about "a fully developed stall"?  No, the point of the exercise is to fly close to the stalling point, so that you learn what it feels like, and so avoid getting into a stall in real flying.  What you wrote is "it really can't be done any other way".  I'm just pointing out that IT CAN, as your airshow example also shows.  Of course it's not usual practice, but there are a lot of things that are possible that aren't usually done.

@GdD: It's simply wrong to say an airliner can't descend "any other way" than by "throttling back the engines and putting the nose down." Airplanes (even airliners!) can absolutely descend by throttling back without putting the nose down. That's not necessarily a stall; it's just some positive angle-of-attack. It's safe and controlled. Your link about why intentional stalls can be impractical doesn't have any bearing, because it's a false dichotomy to say the airliner either has to be nose-down or be in a stall.

AIrcraft usually land into the wind, but your flight landed with a ~5kt tailwind. My hypothesis: The crew may have planned the descent profile so that they would fly past the airport, turn and then land into the wind. At some point they discovered that a straight-in landing would result in an acceptable tailwind. This reduces track length and therefore flight time, but it also meant a steeper descent. The descent speed peaked at over 4000 fpm, which is very high for airline operation.

@EliseBarker: Some pilots have youtube channels where they explain stuff about aviation for a general audience, for example Kelsey, aka 74 Gear has a good sense of humour, and has answered questions from viewers.  (Also some movie reviews explaining how real flying is different from what you see in most Hollywood movies, or what's accurate in movies like Sully).   Learning some more about everything pilots do to fly safely might help you get over some fears.  Maybe including crash investigations to learn what's actually bad.

TL:DR: aviation gets less scary for many people when they learn more about it while sitting comfortably on earth.  And learning some about cabin crew responsibilities, and what they do in an actual emergency, might shed some light on things.

For learning about flight safety procedures and stuff, Mentour Pilot might be a better choice.  Fewer jokes, more focus on how procedures and everything are designed to promote safety, and how aviation has learned from past disasters.

It took me a while to realize that you were not the pilot. That would have worried me...

Nothing out of the ordinary here. You probably arrived at the airport a little bit earlier because ATC allowed your plane to go directly to the runway instead of taking a longer route (as confirmed by the radar data from FlightRadar24). It was probably a quiet moment at the airport and there was no need for your plane to fly to the back of a queue.
Since you were allowed to fly straight to the runway, there was less time to descend, so the descent was a bit steeper than what you're used to. If you're descending steeply, the engines are not needed to maintain speed, and they go really quiet. However, in all likelihood, the only reason they did a steep descent is because they wanted you to get to your destination quicker.
If there's an actual emergency, it is in the crew's best interest to tell everybody. They prefer people to be prepared, even if that means some people may panic. So unless they tell you, there's no emergency. Perhaps they remembered they forgot a part of the safety briefing at takeoff. Or they had some passengers overly protective of their hand luggage (the type that refuses to store their luggage in an overhead compartment six feet away). Unless you asked the crew, we can only guess.

Thats a comfort! We did land 10 mins earlier and NQY is a tiny airport. Thanks for taking the time to reply. One minute we was descending normally and then he went nose down quickly and then levelled up again.  As you say maybe it was a one off with the manual announcement .. one thing- there were two co pilots on that flight. I am such a bad flyer but was much better than a few years ago but now ....

The crew member who made the safety announcement just came up to the front and picked up the "phone" and said it out if the blue...

Sorry, I misread the question. But either way, I think you have no reason for concern. The number of pilots on the flight has no bearing on the safety of the flight.

@Sanchises . The number of pilots on the flight has no bearing on the safety of the flight., true only for 'n >= 2'

The last few minutes of the flight are pretty busy for the cabin crew; if they were expecting to land at time T, and found out at T-20 that it would actually be T-10, then all that work needs to get compressed by 50%. An overall air of urgency will prevail. The minimal announcement about not trying to bring your stuff is probably mandated by regulations, so can't be skipped, even if it comes out hurried and breathless.

@manassehkatz Really, n!=0. All modern planes can be flown by a single pilot if necessary.

@Sanchises I contemplated 'n >= 1'. But while any modern plane can be flown by a single pilot, my understanding is that even in normal (let alone "something suddenly going wrong") situations, both pilot and co-pilot have plenty of things to do during approach & landing. Arguably having only 1 available pilot (due to incapacitation of the other one for any reason) in an airliner that requires 2 pilots for normal passenger operation is "less safe".

@manassehkatz-Moving2Codidact The spare second officer in the jumpseat was pretty clutch in saving Air Astana 1388 from disaster.  This was a case where 3 pilots were decisively more effective than just two.

@J... Similar in the case of https://en.wikipedia.org/wiki/United_Airlines_Flight_232 but arguably "if 2 is the rule, fewer than 2 will cause a significant decrease in safety but more than 2 will not necessarily increase safety".

@manassehkatz-Moving2Codidact Every added redundancy necessarily increases safety.  It's just a question of by how much and whether that's significant and worth the added cost.  Just because you don't need it on every flight doesn't mean it's not there still doing its job just being there in case.

@Sanchises n!=0  Hmm, I'd be extra sure and say n > 0.  I have no idea what having -1 pilots on a plane would look like, but it wouldn't be good...

According to FlightRadar24 here:

at one point your flight was descending at more than 4000 feet per minute. This is a bit faster than usual, especially for the (relatively) low altitude you were at at the time.
However, that is still well within the normal safe flying capabilities of the 737. In an emergency, when the plane needs to get down fast, they will descend at up to about 7000 feet per minute, potentially faster depending on some variables. However, pilots know that fast descent rates are uncomfortable for passengers and are not the most efficient way to fly. So they avoid them whenever they can.
Why did your plane descend faster than usual? I can't be certain but it might be due to a late change of runway direction or traffic conditions, meaning they didn't have as many "track miles" to lose the altitude as they planned. But what they did was a very safe manoeuvre. Whatever the reason, I can pretty much guarantee it was unrelated to the announcement, which was just unfortunate timing.

We weren't told anything, one minute we were going down as usual and the next it was nose down but no faster.. worse was the thick cloud but apparently people on the other side said he was very close to a hill. Im trying not to think of that! The cabin crew bloke I asked didn't really reply as such when  I asked if there was a problem . He just mumbled "all ok" but in fairness he was not great with English

@EliseBarker The fast descend was down to 10,000 ft according to the vertical profile shown in FR24. The tallest mountain in the UK (Ben Nevis) is only 4,411 ft tall (and far away from your flight). So there was definitely no hill anywhere close.

I could not see as it was cloud and all thats in that area are the quarry's so it may have seemed close. I am a terrible panicker and when I felt the force as it descended quickly and someones maltezers came rolling to the front ( I was in seat 2F ) I was absolutely terrified! Thanks for all the info though..

If there were hills/mountains to avoid, @EliseBarker, you would have been climbing not descending.

One thing to keep in mind, most people sitting in the cabin really have no idea what the nose (pitch) is doing unless they look outside. An aircraft isn't just a floor that tips. A pilot can make every loose item in the cabin roll forward simply by slowing down quickly. It's a trick of physics used in amusement park simulators. New pilots fall victim to this trick if they fly into a cloud and ignore their instruments. They keep making adjustments so they feel gravity below them. But gravity feels like any other force so many new pilots fly out of their first cloud completely upside down.

@user253751 the artificial horizon is the instruments. The problem with "feeling gravity" is that a slanted bank combined with sight pitch up will feel like gravity, but keep doing that and you'll eventually be upside down relative to the earth but still feeling the gravity. You can actually fly a plane into the ground and never sense that you're upside down.

@user253751 Here's a video the Australian aviation regulator released on it: https://www.youtube.com/watch?v=pc9xI4kpY4w It's titled "178 seconds to live" for a reason.

@EliseBarker don’t listen to the other passengers. 99% of them have no idea about the safety of airplanes, and the 1% won’t be gossiping about hills

This is known as the graveyard spiral for a good reason: https://en.wikipedia.org/wiki/Graveyard_spiral

She did say "one of the crew members" made that announcement. But I do wonder (since most modern planes, and certainly all airliners, have machine-voice announcements in the cockpit), are there any machine-voice announcements that might be played back in the cabin based on certain conditions being met?

The economics of descent planning
Normally the pilot wants to descent in an economic manner and also try to keep passenger comfort in mind. Let's start with the "economic" descent: An airplane will generally consume least fuel per distance at its "optimum cruising altitude". The exact altitude is dependent on the type of plane, the wind and weight. For a jet like the 737 you flew with it is safe to assume that this optimum altitude is >FL300 (so above 30,000ft / 10km). In cruise your flight was at FL400 so that was probably near the optimum for your specific flight on that day.
As soon as you start your descent to your destination you are leaving that optimum altitude. This is bad. So you want to start your descent as late as possible.
On the other hand, at the end of your flight you still have some "free energy": The potential energy conserved in your altitude. You also want to use that energy as good as you can. Using that energy means to turn your plane into a glider. Theoretically you shut down the engines and glide down to your destination (in reality the engines are not shut down but just set to the lowest possible thrust setting).
Those two factors give you an optimal "top of descent": The point at which you can reduce thrust to minimum setting for the remainder of the flight and still reach your destination by flying with "best glide speed".
Now in reality this is disturbed by a few factors. Mostly "other traffic" is such a factor. Maybe you cannot start your descent at your preferred location because there is traffic below. Or maybe you expect a certain routing, start your descent at the correct place, but then in the middle of the descent ATC gives a you different routing which maybe a shortcut or a detour. In this case you are now "too high" or "too low".
Your particular flight (undesired level off)
In the case of your flight you can see a suspicious "level off" at about 15:29 in FL280:

It is highly likely that the pilots were on their desired flight path, but air traffic controllers did not allow them to descend any further. The most likely reason for this is crossing traffic, but it could also have other reasons like late coordination between controllers etc.
Fixing the undesired level off
Anyhow, what can you do as a pilot in such a situation? You will need to use engine thrust in order to stay in FL280. Then once ATC allows further descent you will be too high due to your level off and you need to somehow get rid of the additional energy you have. From an economic perspective this is really bad, because you are burning fuel unnecessarily.
But the pilot is not powerless. There is a third resource you have: Your speed. In such a level off you can reduce the speed in order to leave your engines at idle (or at least a low setting). Actually you can see a pronounced drop in airspeed on your particular flight, so that is probably what the pilots did.
Then when ATC finally allows further descent, you are now too high and too slow. So it is time to trade altitude for speed. And that will result in a nose down attitude. The pilot with high passenger comfort awareness will do do this trade slowly, gradually picking up speed. However the more economic way is to do this quickly.
Additionally it may well be possible that the pilots could not reduce the speed as much as needed in order to conserve their desired state of energy. Maybe they needed engine thrust nevertheless. In this case even after trading altitude for speed they are still too high. They now need to get rid of this energy somehow. One way to do so is to use the speed brakes. However braking away the energy means the extra energy just goes to waste. Another option is to just fly faster. If you fly faster air resistance increases exponentially, thus you will also waste some energy, but at least you also get a benefit from that procedure: You'll reach your destination earlier. So the pilots might want to fly even faster than normal and that means an even steeper descent.
Managing passenger comfort while trading altitude for speed
In this situation it is likely that the AP (Autopilot) was engaged. In that case the comfort depends on the programming of the AP and inputs the pilot makes. The "simplest" mode would be "level change" (Boeing, on Airbus the equivalent would be called "open descent") and at the same time set a high speed target for the AP. In this case the AP will set engines to idle and then pitch down in order to gain speed. How much the AP pitches down depends primarily on the difference between current speed and the target speed. It is completely safe to engage "level change" mode and immediately set a very high speed target. But it can lead to an uncomfortable pitch down as you have experienced.
There are a few tactics to make this more comfortable. One way is to engage "level change" but gradually increase the speed target for the AP. The speed will build up slower, but the pitch will feel much more comfortable. Another option is to not use "level change" mode but "vertical speed" mode. In this case the pilot typically sets the speed target to a very low value (so that engines are idle) and then set a defined rate at which the plane should descent. This also causes the plane to pick up speed (if the vertical speed target is set high enough) but this happens much smoother. However it also means that the resulting speed is not controlled by the AP anymore. The pilot needs to closely monitor the resulting speed and readjust the vertical speed as needed.
As a side note, if a pilot is new on that particular airplane type (or AP) or did not have such a situation for a long time it may also be that the pilot is surprised by how strong the AP pitches down and might manage this differently the next time. However this does not make the situation unsafe. In a comment to another answer you wrote that there were two co-pilots on board. This MIGHT indicate that this was a training flight. On the first flights of a new co-pilot an additional "safety pilot" is in the cockpit to monitor and assist or (in worst case) take the position of the new pilot. This would support the theory that the extend of the pitch down might have been unintentional.
Conclusion
To conclude: The descent your experienced was likely the result of an ATC descent restriction. The maneuver was safe and probably the most economic thing the pilots could have done. However more comfort would have been possible and the pilots probably put put economic or workload concerns before passenger comfort. At any rate it is unlikely that there was any danger.

Might be worth stressing, that the possible crossing traffic and air traffic control restricting the movement of the aircraft is by no means unusual or risky. It is totally normal and everyday life on the line.

Thanks for taking the time to explain things . Up until about 16 I was fine with flying but then had a break for several years until 6 years ago and I suddenly went in to terrified mode while waiting to get on the plane. .. in a nutshell it took 5 years and numerous sedatives ( never worked ) to build up some confidence and I was doing really well. Never liked take offs but I was ok during the flight until that nose dive !! everyone who replied has made me feel confident enough to fly again I hope,  and I am really glad I found this site. I googled for hours !

@Elise if you broadly studied accidents in all travel modes, and let accurate data guide your thinking... you'd feel safe as houses inflight... a little bit watchful when the airplane is on the ground... but you'd never step into an automobile, again, ever.

lots of stuff rolled to the front

This is a sad but common indicator of how ignorant your fellow passengers were.
Because most people have understandable concerns about being a mile up in a tin can, airlines make the interior feel "homely" and safe.  As a result, people treat it as if they were sat in their armchair at home.  They aren't, and this is dangerous.  If you're driving, you should naturally be aware that random unsecured stuff will fall around when you accelerate, brake or corner; but people seem to forget that this is going to happen in a plane as well.
This is why flight attendants are vital members of the crew when it comes to keeping everyone safe.  There are always a few idiots who think it's perfectly fine to leave bottles, handbags or whatever rolling around on the floor.

I really thought we were crashing

And again, this is a sad but common indicator that people don't actually know what flying feels like.  The worst way to be scared is to not understand what's going on, and being a mile up in a tin can isn't anyone's natural environment.  If your only experience of driving was up and down a 100-mile straight stretch of highway, then braking for traffic lights would feel like you're crashing too - even though it's just normal driving.  That's where you are right now.
If you want to be less scared as a passenger, go up for an air experience flight in a small plane or a glider.  If you pick the right one, you'll even get to fly the plane yourself for a bit.  Sat next to the pilot as they talk you through what they're doing, it'll give you a much better appreciation of what's actually going on.  Then as a passenger in a larger plane, you're in a position to know what's going on and rationalise it to yourself, and that does absolute wonders for keeping yourself calm.
That bump and whirring from the wings after takeoff or on landing approach?  That's the flaps, which you saw the pilot wind out manually on the smaller plane.  A bit of turbulence on a warm day?  Any small plane will be bounced around a bit with thermals, so you've been there and done that.  Tight turns and the wings looking like they're right up and down?  Small planes flick into turns way faster, and can easily turn way tighter.  And because of the size of it, it feels natural rather than dangerous.

Taking a flight in a small aircraft where you A) sit right in the front looking out the front windows (which you cannot do in an airliner), and B) can talk to and watch the pilot (if he's calm, you should be too), is an excellent suggestion!

Do you have any evidence that leaving an object as small as as a water bottle loose is dangerous?  How about in the absence of turbulence?

@AnonymousPhysicist Many people have glass bottles, bought in the terminal. So my evidence is every person who's ever cut themselves on a piece of broken glass, since the invention of glass. ;)

@AnonymousPhysicist : end of dinner one third into the 12 hours night flight, a small glass bottle of wine opened on my aunt's tablet next to me, so I signaled her, but she was so busy enjoying her meal. 2 minutes later, level change, B77W burned enough fuel to climb from FL330 to FL370 and some hazy glows of beacon light outside tells you there are cirrus clouds. Yeah, turbulences, the bottle tipped, now she's covered in blood red. The danger was not the bottle, it was she panicking, though, the bottle rolled somewhere only one flight attendant knows where when we asked for towels.

@Graham People can also get cuts from glass bottles that are not loose.

I've had this happen for urgent situations, where it's important to land quickly even though nothing is wrong with the plane.
One time: there was a strange rattling noise coming from the cargo area.  We made an unplanned landing in a different country so they could investigate.  It turns out some type of hose had come loose, nothing dangerous.
If there's a medical emergency, they'll also want to land quickly.

When we had landed nothing happened as in people being rushed off or anything like that! im very ignorant about the hows and whys of flying but my anxiety is now cruising at about 80,000 feet! i do remember I immediately went on FR24 and a pop up said something like " your flight was alerted by.." and then the flight that did the alerting was highlighted around the sea off South Wales.. I'm none the wiser but it was horrible not knowing and Im grateful  for all the lengthy replies from everyone..


text:
Can you identify this 1920s or 30s biplane?
Can you identify this aircraft from the 1920s or 30s I think? On the back of the photo it says “Taken at Nanking, after flying from Hong Kong to Shanghai”. I don’t know who the pilot is. My grandfather was in the British Fleet Air Arm, so I guess it is one of his friends. There is a distinctive air intake above the propeller which doesn’t match any photos I have seen.

I think this may be an Avro Avian. Wikipedia has a few different illustrations of this (more on Commons) but several types have the pronounced bump of an intake over the propellor; in particular, this 1933 photo of Hélène Boucher is an almost perfect match (shown below).

Agence de presse Mondial Photo-Presse, Public domain, via Wikimedia Commons
I was able to track down a couple of references in the British press to fourteen Cirrus-engined Avians (the same type as Boucher's?) being sold to establish a flying school in Nanking/Nanjing in 1929. One was successfully flown from London by two Chinese and Danish pilots - it took ten weeks of which 21 days were flying time. The others seem to have been shipped and presumably arrived later that year.
It's a bit unclear what happened to them after that, but this photo suggests they ended up at the "Nanyuan Air Force Academy". The description also suggests that site closed in 1928, however - so a bit of a mystery.

Update: in the comments ymb1 picks up that the letters seem to be VR-H (Hong Kong), and mins points out the Avro production list. From that we can see the fourteen Avian IVs in 1929 (ten to "Canton Government", ie the Republic of China, and four to the Chinese Navy) as given in the article, but there are also are a further 34 Avian IVMs with VR-Hxx codes. These were all sold via the Far Eastern Aviation Company of Hong Kong; one is explicitly noted as going to a Hong Kong flying club (VR-HAE) but the others are mostly noted as going to the Government of China. There are also another batch of eleven IVMs for the "Kwangai Air Force" in 1930-32, again via the Far Eastern Aviation Company; this seems to have been one of the smaller independent groups though I cannot work out which one.
My guess would be that this is one of the second batch of Chinese Avians, going to the government in Nanking, and the Hong Kong - Shanghai - Nanking flight was the delivery flight from Hong Kong, where they were imported and assembled?

Spectacular answer!

You can vaguely read some big letters on the underside of the lower wing in the OP's photo, looks like "VD" or maybe "VP", "VR", "VB"?  Might be a clue of something...

@ymb1 Now you've said that, it looks an awful lot like "VR -" on the left and then a faint but distinct "H" on the right - sadly the two identifiying letters are just out of shot.

@mins thankyou!

Some info which could be useful: VR-H series started in March 1930. Avro production list. The flying school could be Far East Flying Training School.

@mins that is very helpful! I think the serial lists strongly suggest it was one of a second batch sold to the Chinese government via Hong Kong, and maybe this was the delivery flight? Have updated.

The mind boggles at just how much information a bunch of experts can extract from one old photo. Congratulations people!


text:
How can I re-certify my PPL?
I have:

a US PPL issued circa 1980 (for about $1600.00 total cost)
120 hours ASEL pilot in command
last flight in 1987
type rated for Cessna 150/152/172/172RGII
30 hours of IFR instruction and flight/hood time
passed IFR course way back then but don't recall taking the test

My pilot log is in another state so I can't confirm test. Not much validity towards IFR rating now? Then my wife somehow got pregnant, more than once.  End of money to fly on. I want to fly again...
Considering how different the aviation world has become (complex rules) or otherwise changed, I'm wondering how much ground and how many hours of recurrency might be in order just to re-certify my PPL VFR? I realize everyone has a different learning curve. And I am in no way as sharp as I was 35 years ago. You senior folks will understand that completely.
Flying/controlling the airplane itself, I believe would not be an issue. But just thinking about all the updated learning of new rules makes me wonder how much it may cost just to be VFR PPL certified again. If I get complex time in a 172 Cutlass does that make me recurrent in 150 thru 172 also?
Looking for thoughts by those who have done it or have taught it to old guys now able to spend on flying again. I would be looking to join a club in SW FL at some point after training. Thanks for any feedback.

The short answer is that you just need to get a medical and get a CFI to sign off on a BFR.  How long it takes the CFI to feel comfortable doing that is the question.

@Jim, and that's a legit answer.  Everything else is advice and opinion, which this site frowns on...

Cessna's don't have a type rating...

I think, going from my somewhat spotty memory of FAA paperwork, that you will also need to jump through some hoops to get an updated physical certificate.  Nothing to do with flying, though: just more "Real ID" stupidity :-(

Welcome to aviation.SE! We have a couple of related questions that you might find interesting: here, here

If you hold an FAA issued PPL from that era, it’s is not subject to any expiration dates or limitations per §61.7 and §61.11.  If you need to check the status of your airman certificate, you may do so using the the FAA’s online airman database.  If you need a replacement airman certificate, you can contact the FAA and request one online for very little charge.
As for legal requirements, you will have to obtain at a minimum a flight review per §61.2(b), §61.56.  The amount of time required to become proficient again as a pilot and satisfactorily pass a flight review varies from person to person, but, as a general rule, anticipate at least one (1) hour of ground and one (1) hour of flight training for every year since you have last exercised pilot in command privileges aboard an airplane.  You will also need to meet the currency requirements to carry passengers aboard your airplane, if you intend to do so per §61.57.
You will also need to obtain at least a new Third Class Medical Certificate.  Unfortunately the time since your last medical certificate expired does not qualify you for use of BasicMed under Part 68.  You can find an Aviation Medical Examiner (AME) here to schedule your flight physical with.
Your old logbook is not required in order to resume flying or work on a flight review, provided your PPL is valid, but it would be indispensable if you’re ever looking to obtain new ratings. Technically pilots are only required to log hours used toward obtaining new ratings or  certificates.  If you do intend to work on an instrument rating, and your old logbook does contain instrument flight hours log dual with a CFII, it would behoove you to obtain that old logbook ASAP.
A Cessna 172RG does not require a type rating in order to fly, but does require a complex airplane endorsement from a flight instructor.  This would most likely be in your old logbook. If you cannot obtain one, they are relatively easy to get from a new flight instructor per §61.31(e).  Your old pilot certificate most likely contains an airplane, single engine land category and class rating on the back of it, which, in conjunction, with a complex endorsement, would allow you to act as PIC aboard an C172RG or similar aircraft.
As for things that have changed since the last time you flew an airplane, Very few new air frames have entered the general aviation market, but onboard systems and avionics have changed quite a bit since the 1980s.  Regulations on flight operations as well as surface movement, runway incursion avoidance, etc. have changed quite a bit since then.  If operating around the Washington DC metro area, you will require additional training prior to flight ops in or around the DC SFRA, which can be done online.
Your best bet would be to contact a competent flight instructor and talk with them about this situation so the two of you can formulate a good game plan to regaining your flight currency. It’s not a test or a pass/fail situation but it will take some time and study on your part.  if you like you can contact me (I’m a current CFI/CFII) and I can offer additional help and give you access to my info archives to better assist you.

As noted in the comments the only legal things you need to take care of are getting a valid medical and a BFR sign off. AOPA has lots of info on getting back into it. There are a few more things to note:

Type rated for Cessna 150/152/172/172RGII

Also as noted in the comments the Cessna's you have listed here dont require a type rating so your license is likely issued for single engine land which allows you to fly other aircraft like the PA-28. You dont need to look specifically for these Cessna's to do your new training in, aside from the fact you may be comfortable with them there is no legal requirement for it.

If I get complex time in a 172 Cutlass does that make me recurrent in 150 thru 172 also

If you are current (BFR + Medical + 3 takeoffs and landings) you are legal to fly single engine land aircraft. Having recent experience in a 172 might might get you legal currency but it does not make you proficient to fly all other Cessna singles.

Passed IFR course way back then but don't recall taking the test

If you never sat for the check ride/written/oral then you don't have an instrument rating but the FAA has digitized most of their records for you to check.
The last thing to consider is that a lot has changed since the 80's. GPS has become a large part of flying and a huge part of IFR flying so you will need to get up to speed on that if you want to get back into instrument flying.

The first answer is a perfect answer. Assuming you have your physical license in your possession, you need a new Medical plus a Flight Review from a CFI, who will decide how much training is required to get you to being proficient and safe.
The flight review also includes an hour of ground time where the CFI will check your knowledge on subject areas that you need to be up to date on to be safe (as opposed to being like a checkride oral where you are quizzed on everything).
You can get a jump-start on the knowledge section by reviewing regulations (pilot currency, etc.), aerodynamics if you are rusty on it (especially stall/spin awareness/avoidance/recovery), performance: practice calculating weight and balance and runway lengths required, weather, weather products (like METARS, TAFs, etc.), airspace (since much has changed).
Check out www.aviationweather.gov  and always check tfr.gov before every flight (click on the button that makes it show you a map of all the current TFRs so you don't have to read the list).
You can download FAA books like the Pilot's Handbook of Aeronautical Knowledge and others for free in pdf form from FAA.gov
The FAA has a "WINGS program", which is online learning that counts toward the ground time requirement for a Flight Review.
https://www.faasafety.gov/WINGS/pub/learn_more.aspx
However, it's been so long since you've been current that the WINGS online learning won't satisfy the 1 hour of ground required for the Flight Review for this first one.
It's been so long that you'll be doing some training- not just a flight review (as you know).
Regarding the aircraft types, as has been said, from a regulatory standpoint little Cessnas don't have type ratings. You should train in whatever type you are most comfortable in.  If that is a C172, use that.  Then if you want to fly something more complex, the FBO you rent if from will give you a checkout on that airplane.
Since you are in Florida (as you already know), you'll want to hit the weather and weather products knowledge hard because of the thunderstorms and all the other nasty stuff associated with that warm unpredictable unstable air down there.
Regarding the instrument rating, your CFI will probably have you start from scratch in order to find out where you are with that, and then fast-forward through whatever you are competent on.  However, even more than VFR skills, the instrument scan really suffers from disuse, so you'll have plenty of time to work on it. Your CFI will also make sure you understand disorientation, unusual attitudes, and how your vestibular system works (more stuff you can review).
You'll want to learn how GPS works. Lots of new cool stuff there with WAAS and GPS approaches.
I don't know what it's like in Florida, but new C172s have been equipped with Garmin G1000 (glass) avionics for so many years now (since 2005) you are going to encounter a lot of those.  of course, there are TONS of 1980s and 1990s and early 2000s Cessnas out there with conventional instruments to fly.  It just depends on what the flight school has of course.
I learned on Piper Seminoles with conventional instruments and then instructed at a school that had a bunch of new Diamond DA40 and DA42s with G1000. The G1000 is fantastic for instrument flying.
For VFR, you should be constantly looking outside for traffic avoidance so it doesn't matter too much what is inside the cockpit if you want to get a lower rental rate on an airplane.
Make sure the CFI makes sure that you get actual crosswind landing and takeoff practice (review the proper flight control inputs, including during taxi).
If you ever have an engine failure right after takeoff, never turn back. Land straight ahead. Maintain best glide speed and don't pull up to go up because you'll just stall (as you already know).
Don't do continued VFR flight into IFR conditions (the most common cause of GA accidents).  Make sure you understand stall and spin avoidance and recovery techniques.
There's no pressure. Look at it all as training, not a test.


text:
Why are thrust reversers not used to slow down to taxi speeds?
In reading this question (Would more throttle when using reverse thrust reduce stopping distance?), it prompted me to remember that on many of my flights (typically on 737s or CRJ type aircraft), it seems that thrust reversers are used for a few seconds after landing, but then are deactivated while the aircraft is still rolling at high speed.  The pilot then utilizes the regular brakes to slow down to taxi speeds.
I am wondering why the pilot does not continue to use thrust reversers down to approximately taxi speeds, to reduce the amount of brake usage (and heating of the brakes) needed.  My only guess would be to possibly avoid the reversers kicking up FOD back into the engine inlets at lower ground speeds, but not sure if that's the real reason or not.

A minimum max reverse power speed is often an airplane operating limitation.  It's mostly related to FOD (mostly sand grains and small gravel) and on some designs there may be compressor stall issues due to flow disruptions.
On the CRJ 700 max reverse is limited to 75kt although you can use up to 60% N1 down to zero speed.  On a 900 you have to be at idle below 60kt.
In practice, you start to come off max reverse during the landing roll transition from high energy to low energy (on the RJs, there is a speed call at 90 kts for this).  You come down to idle not too quickly and linger at idle for a second before stowing them; if you just slam the levers down to stow position, the reversers stow while the fan is still producing a lot of energy and you actually get a little kick of acceleration, which feels like you let off the brakes for a moment.
You can use idle reverse, which gives a little bit of braking, while taxiing if the alternative is riding the brakes and overheating them, say like a taxi along a downhill slope or along a slick icy surface where braking is marginal, and you don't want to taxi single engine, and in a pinch you may use reversers to try you save your butt if you start sliding off an icy taxiway with no braking control.

If FOD is a concern at low speeds, how are aircraft able to do "power back" to reverse at airports without tugs?

You'll see that with turboprops more than fans, but yes you can do it if allowed in the aircraft's limitations and if the operator allows it.  The CRJ's limitations do not allow backing up with reversers at all. If you are allowed to, the FOD risk is very high though especially with wing mounted turbofans. Ramp areas are frequently littered with zipper tabs from luggage, easily sucked up.  The perfect object for causing thousands of dollars of damage to a compressor. A competent captain of something like an EMB190, even if authorized, will use reverse to back up only as an absolute last resort

Most of them aren't able to, or at least aren't allowed to. Note that aircraft that used to do it in the past, like the 727, MD-80 or DC-9, all have fuselage-mounted engines that sit much higher than today's underwing-mounted high-bypass turbofans.

@JörgWMittag EVen on tail mounted engines it can have consequences. We once spent a couple of years trying to figure out why one particular airline was wearing out the spline joints between sections of a rotor far faster than anybody else with the same engine and aircraft type. It turned out they were using full power reverse thrust to power back from the ramp and then full power forward instead of the brakes when they reached the taxiway! Memo to pilots: Don't drive a Fokker F100 plane the same way as would drive an F100 race car ...

@John K, my company operates quite a large fleet of CRJs, and while our SOP prohibits it, the aircraft manuals from Bombardier not only explicitly approve backing up with the reversers, there is an AFM supplement detailing how to do it, in all the variants we operate (200,700,900)

@nexus_2006 my last flight in an RJ was 2012 and I was looking at my old PRM to refresh my memory (which just says "Backing up using thrust reversers is prohibited"), so that's something newer (the AFM supplement tells me the procedure was tacked on, probably due to customer requests).  Thanks for the input.  So does the 900 now allow more than idle reverse below 60kt?

@nexus_2006 BTW does that mean that the 900 can now use more than idle reverse below 60kt?

To be totally honest, I'm not sure what limits are in the AFM for thrust reverse below 60 KIAS, as my company requires idle (preferably stowed) by 60, I just know that the manufacturer has some sort of approved procedure to taxi backwards using the reversers.  I don't know of any (US) operators that do this though.  I'd guess that the procedure is old and still there for historical reasons, operators seem to be trending towards reducing thrust reverser usage.

To avoid kicking up rocks and debris for potential damage and ingestion, along with hot gas ingestion. Also not needed. Kinetic energy is proportional to velocity squared, so once you've knocked off the high velocities, most of the energy is gone. Brakes are fine from there.

I believe its to prevent sucking in hot air from the reverser back into the the inlet.
For example for the JA-37 that is the reason why you are not allowed to thrust up very much at low speeds with reverser on.

Thrust reversers are very effective at high speed and have poor retardation at lower speeds. Using the brakes in the landing roll gives them about a tenth or less of the wear that they get taxing for take-off, and greatly reduces the wear they experience taxying to the terminal.  Paradoxically, using the brakes in landing reduces brake wear compared to not using it at all in the landing rollout.  So the reversers increase your safety margin, which is always a good thing, whilst using the brakes as well reduces brake wear.  There is almost no increase in brake wear if brakes (with or without spoilers/lift dumpers) are used in the landing roll without reversers being deployed. It's debatable whether or not reversers are worth the trouble, but they sure can help when things go wrong.  But as discussed, they also impose their own risks and costs.  Fortunately, they are MELable, and dependant on the airline, locking pins may be carried for pilot use in locking them out if need be for the MEL.


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Why do many stealth aircraft have a similar shape and design?
I have been playing around on a bunch of programs with stealth planes and their general shape. I know that they are required to be flat and have some sort of special material/paint on to 'absorb' the radio waves.
But I have been pondering about the required shape of these aircraft and why the flying wing shape is so widely used (excluding its lift efficiency). Why not some other shape, like a tilted square, triangle, or even a sphere? What makes the general shape of the B-2 and F-117 so common in the design of stealth aircraft?

The b-2 bomber has a very stealthy and very aerodynamic shape. The whole plane is basically a wing there is no fuselage. The reason for this design was actually inspired by a nazi plane concept from ww2. The Nazis designed a plane with a similiar shape but didn't realize it had stealth capabilities. Once the Americans took the design of that fighter we found it had a pretty major stealth advantage over current planes at the time. The f-117 shape is specifically designed to deflect radio waves. All of those corners deflect the waves although it's maneuverability is pretty slow.

The designers for the b-2 went to a museum and saw the concept nazi plane and based there design off of it. The concept plane is called the horton ho 229. It's really fascinating

The f-117 was designed in the late 70's when the main focus was stealth. The main purpose of this fighter was stealth. So all the corners were the way engineers came up with to deflect radio waves. The only problem with it was the fact that It wasn't aerodynamic at all. It completely lacked maneuverability. It was expensive and unaerodynamic so only 64 were built. But was virtually undetectable by radar.

To answer your question. The flying wing is just the most efficient and effective bomber design current day. Now it is possible that we do use other shapes. There have been sightings of triangular shape aircraft in the sky before. Also spheres or flying saucers have been seen on multiple occasions. So I believe the government does use more designs that we just don't know about.

@Ethan The B-2 was not based on the Horton. It was independent. It was based on Northrop's long history working on flying wings, some of which predates the Hortons.

Inspired might be a better word for it. It is true that northern Grumman engineers did go to a museum to see the Horton in person. More of an inspiration then.

@HephaestusAetnaean: First, it is Horten. Next, the earliest Northrop flying wings may predate the latest Horten designs, but Northrop joined the party quite late. If you want to see really early flying wings, search for "Etrich / Wels glider" (1906) or "Dunne" (1910).

@Ethan first, nice to see you again. second, please write an answer in the answer box, not in the comments

Bob put it in an answer for me lol. Yeah nice to see you again.

@PeterKämpf - I'm not denying the existence of other flying wings. I'm countering the extremely common myth that Northrop "based there [sic] design off of [a concept nazi plane in a museum]." Saying they took mere "inspiration" from the "horton [sic] ho 229" is also too generous. "Competitive research" might be more accurate. 1: https://www.youtube.com/watch?v=cWOq0pdXxFU 2: https://www.youtube.com/watch?v=uUNLf9OfWDA 3: https://www.youtube.com/watch?v=GOB45i5BtQQ 4:
https://www.youtube.com/watch?v=GOB45i5BtQQ

First of all, the general idea is to avoid reflection of radar energy back to its source. Next, you want to direct the reflected energy into as few directions as possible in order to dazzle any observer with a momentary bright beam, surrounded by as little reflection as possible. That is the reason for the aligned edges and serrated patterns on stealth designs.
Next, there is quite some variety. How about this one (Northrop Battlefield Surveillance Aircraft eXperimental (BSAX), or Tacit Blue; source):

Or this (McDonnell-Douglas Bird of Prey stealth demonstrator; source):

Or this (BAE Taranis UCAV demonstrator; source):

If you think that all stealth airplanes look the same, maybe you are only looking at those which were designed for the same purpose?

That is a compromise between low observable requirements and traditional aerodynamics.   Actually a B-2 and an F-117 are quite different in terms of configuration. One is flying wing and the other is not.
Flying wings have historically been very popular for low observable use as the absence of a fuselage, empennage, and other structural features decreases the aircraft’s radar signature.  Most low observable UAV aircraft, such as the X-47 and the RQ-175 also use the flying wing configuration in them.

Briefly, the design of stealth aircraft aims to reflect the minimum possible amount of radar energy back towards the radar. This is achieved in two ways; firstly, the aircraft's shape is designed to reflect the radar energy, which is electromagnetic radiation, away from the radar. This is what gives stealth aircraft their distinctive "look". Secondly, the aircraft's structure is designed to absorb radar energy rather than reflecting it as far as possible. This applies to the aircraft's external "skin" and also to the internal structural components. The use of composite materials rather than metal has benefits in this respect.


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How much is a used airliner worth?
The second hand airliner market is active. Some airlines prefer to sell their aircraft within 5 years of purchase, like Ryanair. On the other hand, some airlines prefer to use second hand planes.

What criteria are considered to evaluate second hand airliners for purchase?
How are the used airliners sold to another operator?

I agree with the current "too-broad" close votes as the question stands now. It would be helpful, IMO, to at least narrow the question to a specific airliner if the title question is to be answered. As it stands, the answer would be something like "Somewhere between roughly the value of a new car and $300 million."

I think the first questions has possibly been answered and the second questions is.....way way too broad.

I vote to reopen. Although the 2nd question is still quite broad (possible rephrase would be: "used airliners") the question addresses one area with notoriously little information.

The 2nd question is still a 2nd question and should probably be removed.

HOURS/CYCLES

The single most important factor in the value of an aircraft (generally speaking) is hours. This will almost single handedly define what the plane is worth. When a plane is built all the parts on it have a life time. This is traced through a series of logs for the plane. When a part is at or approaching its life time it must either be rebuilt or replaced. If you are looking at a plane that has high hours/cycles chances are parts on it will need replacing soon. This is costly to the new buyer and will often reflect in a lower sale price. Here in the US commercial aircraft require more frequent inspections than general aviation planes. These inspections are not cheap and a plane that needs inspection when compared to a plane that just came out of inspection will be reflected in the price as well.
There are of course other factors like wear and tear, corrosion (which can be very costly to fix) and interior condition but generally speaking when large planes change hands they are at least partially repainted with the new companies livery and the interiors are often redone.
For some airlines it may be advantageous to buy second hand planes if they are already flying that make/model. Lets say smallTimeAir flies almost exclusively 727-200's this means they have a nice store of parts for that plane and a crew well experienced in fixing them. It will be easier for them to add another 727-200 to the fleet than say an A320 for which they will need new mechanics and parts they don't have. This makes some used airframes desirable to some people.

And of course, the switch from Boeing to Airbus (in this case) would have a fair impact on the pilots as well, probably more so than a switch within Boeing's lineup (because of some of the differences in design philosophies between the two). Even so, it's a good point to consider.


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How to recognise the Tupolev Tu-154, Tu-204, and Tu-334?
Tupolev used to be the one of the largest airliner manufacturer comparable to Boeing and Airbus. However since the dissolution of USSR, its airliner business is declining, and only operated by a few ex-USSR or communist countries' airway. Currently narrowbody Tu154, Tu204 and regional Jet Tu-334 are still active.
How to recognise Tu154, Tu204 and Tu-334, compared to their rivals with similar size?

First, the Russian airplane industry is organized differently from its Western counterpart. While both have research organizations and aircraft manufacturers, in Russia and Ukraine design offices are between both. In Russia, TsAGI does most basic research and develops aerodynamic designs which are then put into fully developed aircraft by the design offices (Antonov in Ukraine, Ilyushin, Tupolev, Mikoyan (MiG), Sukhoi, Yakovlev or Beriev in Russia). The finished designs are then transferred to manufacturing plants like Aviakor in Samara which churn out the actual hardware. If the demand for Tupolevs goes down, Aviakor will switch to Antonovs or Ilyushins, so the fluctuation for products of a particular design office can be evened out.
One consequence of this arrangement is that aerodynamicists have the first say on the shape of the aircraft. Russian designs generally have more refined aerodynamics, at the cost of a higher manufacturing effort.
Older airliners from the Fifties and Sixties were designed with dual use in mind, and many of them had a glazed nose, which makes them easy to distinguish from their contemporaries from the West.
Tu-154
This design from the 1960s is similar to the Hawker-Siddeley Trident or the Boeing 727. Its production surpassed 1000 aircraft and ended only in 2013.

Tu-154 of Uzbekistan Airways (Picture source).
Four items make it easy to identify:

The landing gear uses six-wheel bogies, which is unique among three-engined airliners.
For aerodynamic refinement, heavy use of Küchemann bodies is made in the T-tail intersection and for stowing the landing gear.
The aerodynamic refinement also shows in the length of the conical section of the fuselage, which takes much longer to reach its cylindrical shape. This is a consequence of putting aerodynamics before ease of manufacturing.
The central air intake is of elongated shape, while that of the Boeing 727 is round and the one of the Trident was a heavily rounded triangle.

Tu-204
Intended to replace the Tu-154, this two-engined airliner flew first in 1989 and looks similar to a Boeing 757. It is still in production, but less than 100 have been produced.

The main differences from the Boeing 757 are:

Since the cockpit of the Boeing 757 is identical to that of the Boeing 767, it looks oversized for the narrow-body fuselage of the 757. In comparison, the cockpit windows of the Tu-204 are smaller and look more natural.
The top of the 757 fuselage slopes down over the full length of the vertical tail, whereas the downslope of the Tu-204 fuselage starts only at the rudder.
To distinguish the Tu-204 from an Airbus A320, look at the wheels (four-wheel bogey on the Tupolev, two-wheel gear on the Airbus) or the APU exhaust, which in case of the Tupolev is a small tube sticking slightly out from the fuselage, while the Airbus has a metal-colored cover at the end of the fuselage.
Another difference is the Tu-204's much longer fairing for the wing-fuselage intersection.
Also, the winglet shape is quite different between those three types.

Tu-334
The Tu-334 is a shortened Tu-204 with fuselage-mounted engines. Only two have been built, so the chances to spot it are remote. The new location of the engines allows it to use a very short landing gear, and the shortened fuselage gives it a rather stubby, unique appearance.

Similar airplanes are

Short versions of the DC-9 like the DC-9-10 or the DC-9-15; here the low bypass ratio of the DC-9 engines results in much smaller intakes and longer engine nacelles. Also, the fuselage of the DC-9 is more pointed ahead of the cockpit. The cockpit windows of the DC-9 have a separate window above the regular row of windows for better visibility in steep turns, which is missing in the Tu-334.
Comac/Avic ARJ-21, a Chinese development which is based on the DC-9 fuselage, but has a modern, Antonov-developed wing and high-bypass-ratio engines. Here the upper cockpit windows are missing, so the best way to tell the Tu-334 apart from the ARJ-21 is again the more pointed fuselage nose of the ARJ-21, the bigger fairing of the ARJ-21's wing-fuselage intersection, the lower aspect ratio of the Tu-334 vertical tail and the rear end of the fuselage, which ends with a vertical edge in case of the ARJ-21.

I would argue that the Tu-204 is at least as easy to confuse with an A321 with V2500s as with a B757. In that case, the two main differences are probably the two-wheel bogies and the much smaller vertical stabilizer on the Airbus model. And possibly the door arrangement.

I don't know why but Tu-334 looks like the cutest airplane out there. You have to agree.

@Ethan Beauty or cuteness is, I think, in the eye of the beholder. When I saw the pic of the Tu-334 (before I read your comment), the first thing I thought of was an overweight human baby, and I am one of these people who are of the mind that all human babies are basically unattractive creatures, a view that my wife feels indicates that I have no taste or sentiment.

@JulianHzg the Tu-204 looks pretty similar to the A320 India Edition as well :)

@MikeFoxtrot: An A320 with a four-wheel bogie - now that is interesting!

@Terry Cuteness it has a short fueslauge and that those tiny landing gear

@PeterKämpf -- if the Russian designs tend to be more refined aerodynamically, what keeps them from matching the West when it comes to fuel efficiency, or are the current Russian designs on par with what we're building on this side of the planet in that regard?

@UnrecognizedFallingObject My impression is that Russian designs, at least the older ones, are built far more ruggedly than western designs. Hence they are heavier and that degrades their fuel efficiency. I know from experience that Russian airfields in Siberia were, frankly, not suitable for continual usage by western aircraft. We had to stop refueling 747-200 freighters at Kharbarovsk because the runway design resulted in a runway so rough that it was literally shaking our aircraft to pieces and upping our maintenance costs. Consider making your comment a full fledged question.

@UnrecognizedFallingObject, in addition to what Terry said (cf MTOW Tu-154M vs A320: 104 tonnes vs 78 t, for the same 180 pax and comparable range), the engine parameters were, perhaps, most lacking. That said, Tu-204 is generally on a par with the similar class 757 and A320 in terms of fuel efficiency.

@UnrecognizedFallingObject in addition to the previous comment, also bear in mind that Soviet designs are according to different ideas, not better ideas. There are often more ways than one to do something, with Soviet design philosophy frequently leading to quite different results from western design philosophy in order to meet the same requirements (or quite different requirements of course).

That Tu-334 looks like it's dancing!

Tu-154 has three rear-mounted engines and triple-axle, six wheel landing gear.
Tu-204 is perhaps the only slightly difficult one in your list. Short stubby nose and rather long engine cowlings. Mostly operated by non-western carriers.
Tu-334 is cancelled.


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Why both ICAO and IATA headquarters are located in Montreal?
Montreal is not large city like Paris and New York, nor a important place in aviation history like Kitty Hawk(Wright brothers first flight) or Friedrichshafen (Zeppelin airship first flight). Why Montreal is being chosen as the headquarters of 2 biggest aviation organization.

While there may be an interesting answer to this question, it's probably not on topic here.

It should be noted that both organisations have moved HQ around the world a number of times.

Pure speculation on my side, but being a bilingual city (covering two of the organisation's five official languages) must also be an advantage when hosting a global organisation. Not the deciding factor, but nevertheless an advantage in the negotiations.

ICAO is headquartered in Montreal because that was the result of a vote by the founding members (PICAO is Provisional ICAO):

Why was Montreal selected? While insisting on the excellent
  hospitality offered since of the beginnings of PICAO by the federal,
  provincial and municipal authorities, the delegates described Montreal
  like a roundabout of the international means of communication and a
  strategic centre with a formidable economic, scientific, technical and
  aeronautical expansion being felt for a few years. One insisted on the
  vast spaces of the Canadian territory, offering unlimited
  possibilities for the scientific and practical experiments in the
  field of aviation. Moreover, PICAO was to be established as close as
  possible to the central head office of the United Nations.

And IATA is in Montreal because its founding statutes said that it must be in the same location as ICAO:

Article II of the IATA 1945 Statutes states that “The Head Office of
  this Association shall be maintained in the city in which the
  headquarters of the International Civil Aviation Organization is
  located.”; this article was later amended to leave an opening for a
  possible other place as determined by the General Meeting

+1 for providing sources (and interesting ones, too), but they are written in Comic Sans! Does that really count as a reference?

@Monolo :-) Well, the professionals seem to think it has its uses

In addition to Pondlife's answer, it may be worth noting that Montreal is an important place in aviation history as the Convention for the Unification of Certain Rules for International Carriage by Air (now known as the Montreal Convention) was signed there.
https://en.wikipedia.org/wiki/Montreal_Convention
http://www.iata.org/policy/pages/mc99.aspx

That convention was signed in 1999, so those organizations had already been in Montreal for over 50 years at that point.

@pondlife I know, and I accept your answer as the correct one, I still felt it important to point out that Montreal has a rather large significance in aviation history...

Isn't it far more likely that the Montreal Convention was signed in Montreal because it is the ICAO headquarters rather than the other way around?

@Minnie Yes, absolutely, but I would say this should be a comment: it's interesting and relevant, but it doesn't actually answer the question

@Pondlife understood! i couldn't post comments when i posted this because i didn't have enough points! in future i will keep it in comments!


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Can Somebody use Takekoputa to fly?
Takekoputa(タケコプター) is one of the most famous and common gadget in the Japanese manga series Doraemon.
Regardless the power issue, Can it be used to fly in real world, as like as in the animation?

Wow!!! I love Doraemon!!

in some countries, its also known as the 'bamboo copter' .. Anyways, I love that!!

In a manner of speaking yes (although its highly unlikely). If the propellor on his head can generate enough lift to get his mass off the ground there is nothing to say he cant fly. That does not mean that the flight will be very stable or controllable but it may lift off. Since the animal does not have the equivalent of a tail rotor the torque effect generated from the propellor may spin him around. It does appear there may be flyable toy versions

Although for what its worth there is no identifiable power plant that is spinning this head propellor...

Doraemon is actually a robot, so presumably the power plant is internal.  Of course, this particular show is aimed at children, so relevant details are usually light...

I know almost nothing of aviation besides being a minor fan of planes and airshows, but this question tickled me enough to sign up, just to say: Could Doraemon be using a tip jet rotor (https://en.wikipedia.org/wiki/Tip_jet) to get around the torque issue?

Yes, Doraemon is a robot. But Nobita, Shizuka and Giant are presumably children. A great show anyway :)

@vasin you forgot Sunio.. That's not fair..!!

I assume that the thing on his head is a propellor
If so, then in theory yes, it could fly. If the propellor rotates fast enough, and the rest of him is light enough.
Note that his body, however, would rotate in the opposite direction to the propellor, likely making him uncontrollable.
In theory he could lift off the ground, in practice he would almost certainly be uncontrollable

Could Doraemon be using a tip jet rotor (https://en.wikipedia.org/wiki/Tip_jet) to get around the torque issue?

Yes, or two contra-rotating rotors, perhaps - although they would appear to be very close together, I see no reason why it's any less plausible than the rest :) to rotate fast enough they would have t be supremely well engineered anyway. Perhaps the rotor even alternates direction

Or he could use a reaction wheel in his body to counter torque :)

If we're assuming that thing on its head is a propeller I have to assume the big red ball on its tail is the required anti-collision light :)


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Does the size of code F aircraft parking apron enough for 2 code C plane?
When I look at Inner Thames Estuary Airport (Isle of Grain) masterplan, they shows a funny figure about the terminals layout.

The report describes that  It shows the ability for most
stands to handle either a large wide bodied (Code E/F) aircraft or two narrow bodied (Code C) aircraft.
The question is, is it true?

This type of parking system is called MARS (Multi Aircraft (or Apron) Ramp System) and is being used or explored by many airports.
You can see markings for them on the ground at CLE.  Here is a google maps link to one of the stand areas.  CLE terminal
Here is an article on the stands.


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How far can Boeing 777-200LR fly?
The diagram shows the B777-200LR Payload/Range for 0.84 Mach Cruise (P.41 of Source)

The maximum payload range is around 7600 nmi, and after that payload have to be reduced in order to increase range. While the Operating empty weight of 777-200LR is 320Klbs, the horizontal-coordinate(range) of the diagram is around 10500nmi at 350Klbs, and there is a gap of 30Klbs.
Does that mean B777-200LR has theoretical maximum range over 10500 nmi if OEW plus payload is below 350Klbs? And how far can it fly potentially?

Yes

Not really understanding the question because you have already stated the maximum range for the boeing 777-200LR

@fooot - make that an answer. (Might need more than the one word, though... ;)

The vertical axis starts at 350 Klbs since the Boeing 777 is made to transport payload, not just itself. Any operator will be interested more in the upper part of the diagram, because only then the aircraft will earn money. This explains the gap of 30 Klbs - the people for whom this chart was made are simply not interested in the range without payload.
The range varies with flight parameters, and the upper left corner shows the most important ones, albeit in quite imprecise terms. If the flight speed is reduced, range will become higher until the aircraft flies at optimum range conditions. Airlines like to fly their aircraft faster that that to optimize transport performance (the maximum product of speed and payload relative to operating cost). If power extraction and air condition are run at their bare minimum, again less fuel will be needed per mile of flight. Flown this way, the 777 will easily fly more than 10500 nm with a zero-fuel weight (OEW + payload) of 350,000 lbs.
To eke out the maximum possible range, high-density fuel is used and the aircraft is flown at an optimum altitude and speed for range. The records which have been set this way (11,664 nm for the 777-200ER), however, are of little relevance to everyday operation. The longest commercial flight of that type will be the Dubai-Panama City connection of 7,463 nm which Emirates will begin to serve on February 1, 2016.

Plus that nobody would be interested in flying any further than half the circumference of the earth. You simply fly the other way around...

@DeltaLima: I guess that Boeing marketing will be very keen to surpass any Airbus record and vice versa, whatever the practical relevance of that record. But beyond those two organizations, you are absolutely right.

@DeltaLima That would be true in most circumstances, but wind could theoretically make it faster to fly a bit more than halfway around if the city pair in question was already close to being on opposite sides of the planet. Flights from Asia to North America routinely fly hundreds of miles farther than the shortest distance in order to use the Northern polar jet stream, for example. Granted, it might be harder to find similar conditions on routes between near-antipodal city pairs.

@DeltaLima You also have to keep in mind that airspace isn't always available for use.  So you may end up flying the "long way around" just because the shorter route has a war going on in the middle of it.

@reirab, "shorter" here needs to be understood as airspeed times time, so tailwind makes the distance "shorter" and headwind makes it "longer". The chart only shows distance with no wind and wind correction has to be applied and is rather significant. And in that respect, the route with more favorable wind is "shorter".

The longest official non-stop flight by a commercial jet was a 777-200LR flight  from Hong Kong to London in 2005 (without passengers). It was 13,422 miles (11,768 nm, more than 21,000 km).

Given that the two furthest point on Earth are 20037 km apart, this can't be correct. And the London - Hong Kong distance is far less, about 11000 km.
The furthest cities are in fact 19996 km apart (Rosario - Xinghua) http://furthestcity.com/ So the range of the 777-200LR is just not enough between any two cities. But almost :)

@CsongorSzíjjártó The Wikipedia page (citing the NY Times article) clarifies that they flew eastward from Hong Kong, which is not the shorter route that you are measuring.


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What is the rotor speed of an EC135/H135 helicopter?
I need the Eurocopter EC135's rotor speed to estimate its natural frequencies. I checked the helicopter TCDS but I only find there percentage values. For example for the P1 variant: 104% Max and 95% Min. This is percentage of what? In other helicopters I normally get concrete values in RPM.

The main rotor speed (100%) of the EC-135 is 395 RPM.

Thanks a lot. Interesting that the Wikipedia in german as it and in english doesn't. I had already stated this situation before.

I don't have an exact answer for the EC135, but in most helis, its somewhere arond 400RPM. Remember that the tips of the rotors cannot go supersonic, so its dependent on rotor diameter